Net Income (Loss) per Common Share - Reconciliation between basic and diluted net income per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2016	Jul. 31, 2015
Earnings Per Share [Abstract]
Net income (loss) attributable to G-III	$ (1,293)	$ 12,453	$ 1,478	$ 19,213
Basic net income (loss) per share:
Basic common shares	45,667	45,073	45,601	45,020
Basic net income (loss) per share (in dollars per share)	$ (0.03)	$ 0.28	$ 0.03	$ 0.43
Diluted net income per share:
Basic common shares	45,667	45,073	45,601	45,020
Diluted Restricted stock awards and stock options		1,289	1,366	1,269
Diluted common shares	45,667	46,362	46,967	46,289
Diluted net income per share (in dollars per share)	$ (0.03)	$ 0.27	$ 0.03	$ 0.42